Method of recovering metal carbonyls from gases



y 1961 E. R. BREINING ET AL 2,985,509

METHOD OF RECOVERING METAL CARBONYLS FROM GASES Filed Feb. 24, 1958 2 Sheets-Sheet 1 FIG-I METALLIZING GAS EXHAUST PPT AGENT SEPARATION OF PPT-COND'ENSED METALLIZING GAS DRY'I NG AGENT DRIED CONDENSED METALLIZING GAS STORAGE 1N VENTORS WILBUR M. BOLTON ELMER ROBERT BREINING ATTOR NEYS y 1961 E. R. BREINING ET AL 2,985,509

METHOD OF RECOVERING METAL CARBOIYLS FROM GASES Filed Feb. 24, 1958 2 Sheets-Sheet 2 FIG-2 l LIQUID NICKEL CARBONYL FIG-3 5 INVENTORS fi l% i L WILBUR M. aourou CARBQNYL ELMER ROBERT BREINING .8 Wfw ATTORNEYS United States Patent A I METHOD OF RECOVERING METAL CARBONYLS FROM GASES Elmer Robert Breining, Dayton, and Wilbur M. Bolton, Piqua, Ohio, assignors, by mesne assignments, to Union Carbide Corporation, New York, N.Y., a corporation of New York Filed Feb. 24, 1958, Ser. No. 716,953

7 Claims. (Cl. 23-203) This invention relates to the recovery and purifying of condensab-le metal bearing compounds and particularly to the recovery of such compounds from the exhaust gases of metallizing operations employing heat decomposable metal bearing constituents.

Heretofore the recovery of metal bearing compounds such as nickel carbonyl has been eifected through the medium of relatively .expensive equipment utilizing refrigeration techniques. It is a purpose of this invention to provide a method of recovery which is efficient and economical and thus contributes to the overall success of the metallizing operation; which does not require a costly initial installation or complex equipment; and which produces a recovered product free of contamination.

It is yet another purpose of this invention to provide a novel process for the recovery of metallic organics.

In a preferred embodiment of the invention nickel carbonyl is subjected to the recovery operation. Nickel carbonyl, which at room temperature is a liquid, is commonly employed in metallizing by thermal decomposition of the carbonyl in contact with the heated substrate to be metallized. Frequently such decomposition is incomplete, and undecomposed carbonyl, together with products of decomposition such as CO, and carrier gases such as CO and N form the exhaust gases of the operation. Carbonyl recovery is important as many of the carbonyls are expensive and even in the case of nickel carbonyl efiicient recovery is an important factor in commercial aspects of the operation. The exhaust gases of such procedure in the practice of the invention are preferably passed into a liquid, such as water at relatively low temperature to eifect condensation of the carbonyl; being insoluble and heavier than water the condenser carbonyl is readily separable from the water, dried and passed to storage for further use in metallizing.

The invention will be more fully understood by reference to the following detailed description and accompanying drawing wherein:

Figure 1 is a flowsheet illustrating generally the process of invention;

Figure 2 illustrates diagrammatically one apparatus arrangement for the practice of the invention; and

Figure 3 illustrates a modification of the apparatus arrangement of Figure 2 and particularly illustrates a novel mode of controlling the waste waters which may contain some small amount of carbonyl.

In the drawings similar numerals where practicable have been employed to designate corresponding parts.

Also, while this invention is particularly described with respect to nickel carbonyl and water as the insolubilizing or precipitating agent, it will be understood that other carbonyls, particularly those which are liquid at normal temperatures, may be employed in the procedure.

Referring first to Figure 1, which is a flowsheet, it will be noted that the metallizing gas, which is included in the exhaust :from a metallizing operation, is directed to an insolubilizing agent which eifects condensation of the gas and permits separation of the condensate from the in- Patented May 23, 1961 solubilizing agent by gravity. At separation the condensed metallizing gas is dried and then passed to storage. It will be understood that the condensed gas may be immediately reused in a metallizing process, if so desired.

Referring now to Figure 2, the numeral 1 designates a conduit having a valve 2 which is communicable with a metallizing chamber, a fragment of which is indicated by the numeral 3. Accordingly gases emanating from the chamber 3, as indicated by the arrow, will pass through the conduit 1 and the depending portion thereof to the interior of a tank 4, which is sealed by a suitable closure designated at 5. Surrounding the tank 4 is a water jacket 6 which may be utilized for cooling the interior of the contents of the tank 4 if necessary. Usually the contents of the tank will tend to be somewhat warm since the gases entering are generally hot as they leave the metallizing chamber at about -100 F.

The numeral 7 designates an inlet pipe having a valve 8 through which water may be introduced to the tank 4. An outlet pipe 9 having a valve 10, and in the nature of an overflow, is provided in the upper portions of the tank 4. The inlet to the water jacket is indicated at 11 and is provided with a suitable valve 12. The outlet for the jacket is designated at 13 and has a valve indicated at 14.

In the upper reaches of the tank and preferably extending through the closure 5 is a conduit 15 having a valve 16 and which conduit leads to the exhaust of the recovery system. Such exhaust as indicated in Figure 2 may be a vent to an off-gas burner.

With the equipment thus far described it will be apparent that exhaust gases flowing from the metallizing chamber 3 through the conduit 1 will pass into the water contained in the tank 4. Insoluble compounds condensible at the temperature of the water to the liquid state will tend to separate out in the tank 4. In the case of nickel carbonyl the temperature of the water is preferably maintained slightly above the freezing point of water (32 F.) and the nickel carbonyl, as indicated by the liquid, will separate to the bottom of the tank 4, carrying with it some slight amount of water.

The exhaust gases from the plating chamber will gen-. 'erally contain carbon monoxide and other products of decomposition, depending upon the specific metallizing operation; also, in such operations a carrier gas, such as nitrogen, argon or carbon dioxide, is customarily employed, and such constituents will, of course, be present in the exhaust gas going to the water in the tank 4. While these gases will dissolve to some extent, the water will become saturated therewith and a vapor pressure of such gas is built up above the water and the gases flow through conduit 15 and valve 16 to the off-gas burner and into discharge. Gases such as carbon monoxide will be oxidized and rendered non-injurious by the off-gas burner. The liquid nickel carbonyl being heavier than water separates therefrom readily as illustrated in Figure 2.

'Thebottom of tank 4 is suitably tapered as indicated at 17 and directs the liquid carbonyl to a depending conduit 18 having a valve 19 and a sight glass 20. A branch conduit 21 having a valve 22 provides for draining of the water from the tank 4 at the completion of an operation, for example. Another branch conduit below the sight glass 20 and designated at 23 has valves 24 and 25 that communicate with an interphase tank 26 provided with an outlet 27. This interphase tank 26 may be utilized to assist in the mechanical removal of water fromthe carbonyl as the interphase or boundary layers are approached in a mechanical separation of the carbonyl well as The conduit '18 is provided with a valve 28 through which flow of the nickel carbonyl may be directed to a tank 30 having a cover 29- throughwhich theconduit passes. The tank 30 is suitably surrounded with a heat ing jacket 31. In addition the tank has a stirrer 32 and an access hole 33 through which a chemically inert drying agent, such as calcium chloride, calcium sulfate, phosphorous pentoxide, silica gel, activated alumina, or other drying agents, may be passed to within the tank. The numeral 34 in Figure 2 designates an inlet conduit for a gas such as carbon dioxide, while at 35 there is designated a pressure gauge.

Supported by the cover 29' is a reflux condenser 37 which communicates with a conduit 38 having a valve 39 and through which gases may flow to an oif-gas burner. The numeral 40 designates a jacket surrounding the reflux condenser and which jacket has an outlet 41 and an inlet 42 for the flow of cooling water through the jacket.

The outlet 43 through which the dried carbonyl is to pass to storage is provided with a filter 44, which is efiectiveto screen out small particles which might become entrained in the liquid. The numeral 45 designates particles of the drying agent, such as calcium chloride, and

provision is made with a pipe 46 having a valve 47 for the removal of constituents through the base of the tank 30 when so desired.

Referring now to the liquid nickel carbonyl within the tank 4, such is separable readily by gravity from the water and may be passed through the conduit 18 to the tank 30 wherein it is mixed with the drying agent, for example, calcium chloride. Stirrer 32 provides for good contact of the liquid carbonyls with the calcium chloride particles and is effective to achieve pick up of any water retained by the carbonyl.

The reflux condenser inhibits the loss of carbonyl during the period when the combination is in contact with the drying agent. Normally heating is not necessary, but if gently used may speed drying time. The reflux condenser will, of course, pass any gases, such as carbon monoxide or carbon dioxide, which may have been entrained in the liquid carbonyl. Suitably the reflux condenser operates at about zero degrees C.

Where calcium chloride is employed as the drying agent it is preferable, before permittingthe passage of carbonyl through the valve 48 to storage, to allow the particles of the drying agent to settle out. Such may be done by shutting off the stirrer 32 and permitting the calcium chloride particles to settle out.

Removal of the liquid carbonyl from the tank 30, achieved by pressuring carbon dioxide or other inert gas through the conduit 34 to the surface of the liquid carbonyl within the tank 30, the carbonyl then flowing under the applied pressure through the upstanding arm of the conduit 43 and the valve 48 to storage. a 1

A modification of the apparatus of Figure 2 is illustrated in Figure 3, and this modification particularly relates to means for destroying any carbonyl which may I exist in waste waters of the system, and also to a slight modification of the mode of operation of the system.

Referring to this latter feature, while the procedure of Figure 2 is essentially static, the operation of the equipment of Figure 3 provides for a continuous trickle of water through the system. Thus in Figure 3, with the valve 19 closed, water may be passed continuously through the conduit 7 and valve 8 to the tank 4. This flow. should be slow and the tank 4 will soon become filled. The exhaust gases entering the water through the conduit 1 will have the liquid carbonyl condensed therefrom, as already described in connection with Figure 2. However, a slow trickle of water will also pass outwardly through the conduit 15 and valve 16 and this water, as dissolved gases, may include some slight amount of nickel carbonylr V To remove the nickel carbonyl from this exhaust the conduit 15 may have a depending portion 49 passed into a water solution of an oxidizing agent indicated at 50. A tank 51 having a cover 52 retains the oxidizing agent, and an access hole 53 is provided in the cover 52 for the provision of solid material-to within the tank 51.

A The numeral 54 in Figure 3 indicates an exhaust conduit having a check valve 55 and throughwhichIgasei such as carbon dioxide, may be passed to the atmosphere upon the buildup of pressure within the tank 51.. Oxidizing agents, such as chlorine, are passed to the tank 51 through the conduit 56; conduit 57 is provided for supplying Water to the tank 51. The exhaust line from the tank is indicated at58, in which line control valve 59 is provided.

In the operation of this apparatus the liquid carbonyl, as already noted, will settle out in the tank 4, as described in connection with Figure 2. However, the flow of water through the conduit 15 may comprise some nickel carbonyl.

Whilean oxidizing agent, such as chlorine, is supplied through the line 56 to the water Within the tank 51 a chemical reaction between the carbonyl, chlorine and water occurs, resulting in the evolution of carbon dioxide and the formation of hydrochloric acid and nickel chloride. Suitably the oxidizing agent has been made alkaline by the provision through the access hole 53 ofsodium hydroxide, for example, and this sodium hydroxide reacts .with the HCl to neutralize the same. The nickel basic chloride is then substantially passedas a sludge with the solution through the line 58.

In an alternative procedure for drying the carbonyl after its separation or settling in the tank 4, the carbonyl may be cooled down to a temperature at which the water will freeze out while the carbonyl remains a liquid. Such temperature is preferably on the order of 10-20 F. since the carbonyl freezes at -13 F. while the, water, of course freezesat32F. 1

While such separation procedure is advantageous, complete separation generally requires more thanone freezing operation, that is, the separation is fractional. ,Accordingly it requires a longer period of time generally than the drying procedure of Figure 2. g I Other specific compounds which maybe recovered in accordance with the invention are: iron pentacarbonyl, molybdenum carbonyl, chromium carbonyl and tungsten carbonyl. The pentacarbonyl of iron is a liquid and accordingly is treatable in the same manner as described in conjunction with nickel carbonyL. The hexacarbonyl of molybdenum, chromium and tungsten are, however, solids'andare most suitably separable by thefreezing process 'when water is employed as the precipitating or insolubilizing agent. a v 1 Other precipitating or insolubilizing agents include: methyl alcohol, ethyl alcohol, propyl alcohol and isopropyl alcohol.

' to modification in order to adapt it to different usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims;- 7

What is claimed is: i 3 7 1. The process ofrecovering nickel carbonyl in the liquid form from the exhaust gases of gas plating metallizing operations, which recovery process comprises the steps of: flowing the exhaust {gases with the nickel carbonyl therein into water maintained at a temperature .sufiicient to condense the nickel carbonyl while the others of the exhaust gases remain uhcondensed} settling the liquid condensed nickel carbonyl bygra'vity to separate the liquid carbonyl from the water, draining the liquid carbonyl from the water, and thereafter drying the liquid carbonyl to free it from any small amount of water remaining all without decomposition of the nickel carbonyl.

2. The process of continuously recovering nickel carbonyl from the exhaust gases of gas plating metallizing operations which comprises the steps of: continuously flowing the exhaust gases of the metallizing operation including undecomposed gaseous nickel carbonyl into a tank of water, the water being maintained at a temperature such that the gaseous nickel carbonyl will condense to the liquid form while the remainder of the exhaust gases remain uncondensed, continuously flowing the water to an oxidizing chamber while the condensed nickel carbonyl remains in the tank, oxidizing the exhaust gases and carbonyl in the water in the oxidizing chamber to cause evolution of carbon dioxide and the precipitation of a nickel component of the nickel carbonyl, and removing the liquid carbonyl from the tank and from the precipitating agent in the tank while the precipitating agent flows to the oxidizing chamber.

3. The process of recovering heat decomposable metal bearing gaseous carbonyls from the exhaust gases of gas plating metallizing operations which comprises the steps of: flowing the exhaust gases containing heat decomposable metal bearing carbonyl into water in which the heat decomposable metal bearing component is substantially insoluble while maintaining the temperature of the water sufliciently low to condense the metal bearing gas but not others of the exhaust gases, permitting the uncondensed and undissolved exhaust gases to escape, and thereafter freezing the water and then separating the frozen material from the carbonyl all without decomposition of the heat decomposable metal bearing compound.

4. The process of recovering nickel carbonyl from the exhaust gases of gas plating metallizing operations, which recovery process comprises the steps of: flowing the exhaust gases containing nickel carbonyl into water while maintaining the temperature of the water sufiiciently low to condense the nickel carbonyl, permitting the heavier nickel carbonyl to separate under the influence of gravity from the water, draining the liquid carbonyl from the water and to a drying agent in solid form, which drying agent is capable of picking up water, mixing the drying agent thoroughly with the liquid nickel carbonyl, and thereafter separating the liquid nickel carbonyl from the drying agent all without decomposition of the nickel carbonyl.

5. The process of recovering nickel carbonyl from the exhaust gases of gas plating metallizing operations, which recovery process comprises the steps of: flowing the exhaust gases containing nickel carbonyl into water while maintaining the temperature of the water sufliciently low to condense the nickel carbonyl, permitting the heavier nickel carbonyl to separate under the influence of gravity from the water, draining the liquid carbonyl from the water and to a drying agent in solid form, which drying agent is capable of picking up water, mixing the drying agent thoroughly with the liquid nickel carbonyl, and thereafter separating the liquid nickel carbonyl from the drying agent by pressuring with an inert gas the liquid nickel carbonyl to effect removal of the carbonyl from the drying agent against the action of gravity all without decomposition of the nickel carbonyl.

6. The process of recovering heat-decomposable metal bearing gaseous carbonyls from gases containing the same, which comprises the steps of flowing said gases containing heat decomposable metal bearing carbonyl into water in which the heat decomposable metal bearing component is substantially insoluble while maintaining the temperature of the Water sufficiently low to condense the metal bearing gas, and exhausting the uncondensed and undissolved gases, and thereafter freezing the water and then separating the frozen material from the carbonyl to recover said metal bearing carbonyl.

7. The process of recovering metal carbonyl from gases containing the same, said process comprising the steps of flowing the gases containing metal carbonyl into water while maintaining the temperature of the water sufiiciently low to condense the metal carbonyl, permitting the heavier metal carbonyl to separate under the influence of gravity from the water, draining the liquid carbonyl from the water and contacting the same with a drying agent which absorbs water, mixing said drying agent thoroughly with the liquid carbonyl, and thereafter separating the liquid carbonyl from the drying agent without decomposition of said metal carbonyl.

References Cited in the file of this patent UNITED STATES PATENTS 1,251,202 Ellis Dec. 25, 1917 2,254,158 Simpson Aug. 26, 1941 2,516,058 Lander July 18, 1950 2,818,351 Nack et a1. Dec. 31, 1957 2,847,320 Bullofi Aug. 12, 1958 

1. THE PROCESS OF RECOVERING NICKEL CARBONYL IN THE LIQUID FORM FROM THE EXHAUST GASES OF GAS PLATING METALLIZING OPERATIONS, WHICH RECOVERY PROCESS COMPRISES THE STEPS OF: FLOWING THE EXHAUST GASES WITH THE NICKEL CARBONYL THEREIN INTO WATER MAINTAINED AT A TEMPERATURE SUFFICIENT TO CONDENSE THE NICKEL CARBONYL WHILE THE OTHERS OF THE EXHAUST GASES REMAIN UNCONDENSED, SETTLING THE LIQUID CONDENSED NICKEL CARBONYL BY GRAVITY TO SEPARATE THE LIQUID CARBONYL FROM THE WATER, DRAINING THE LIQUID CARBONYL FROM THE WATER, AND THEREAFTER DRYING THE LIQUID CARBONYL TO FREE IT FROM ANY SMALL AMOUNT OF WATER REMAINING ALL WITHOUT DECOMPOSITION OF THE NICKEL CARBONYL. 